Fabric conditioning compositions are often used to deposit a fabric softening compound onto fabrics. These are usually rinse added fabric conditioning compositions. Typically, such compositions comprise a fabric softening agent dispersed in water. The fabric softening agent may be included at up to 7.5% by weight, in which case the compositions are considered dilute, or at levels from 7.5% to 60% by weight, in which case the compositions are considered concentrated.
Concentrated fabric conditioning compositions can suffer, and indeed are much more likely than dilute compositions to suffer from problems of instability both immediately after the composition is formed and during longer term storage.
Instability can manifest itself as a thickening of the composition. This thickening can occur to a level at which the composition is no longer pourable or dispersible in use, and, can even lead to the formation of an irreversible gel.
Such thickening is very undesirable because the composition can thereafter no longer be conveniently used, for example unpleasant residues can be left in the dispenser drawer of the washing machine and/or it is unattractive to the consumer.
Instability is particularly a problem when compositions are stored at high temperature, e.g. above 30° C.
It is obviously highly desirable for any fabric conditioning composition to provide excellent softening. It is known that better softening can be achieved using hardened (i.e. saturated) softening compounds instead of unsaturated or partially unsaturated softening compounds.
It is also desirable to use hardened (saturated) softening compounds as they are believed to have less base odour than unsaturated softening compounds, especially for TEA quats.
However, conditioning compositions comprising hardened softening compounds have been found in practice to be harder to formulate than those containing unsaturated or partially unsaturated softening compounds. For instance, additional viscosity modifiers and/or stabilisers not required when using unsaturated or partially unsaturated softening compounds are usually required in order to achieve a viscosity desirable to consumers, such as a thick, pourable liquid.
It is suggested that the viscosity of concentrated conditioning compositions comprising hardened softening compounds can be modified using nonionic surfactants. However, large amounts of such agents are typically required. Typically, they have to be included at levels in excess of 1.5% by weight, based on the total weight of the composition, and because such ingredients are expensive, their addition increases the cost of fabric conditioning compositions which include them.
This is especially true for compositions comprising hardened ester-linked quaternary ammonium softening compounds, in particular triethanolamine-based quaternary ammonium compounds (hereinafter referred to as ‘TEA quats’).
The present invention thus sets out to provide methods of preparing concentrated fabric conditioning compositions, and compositions prepared by said methods, which achieve viscosities desirable to consumers without the need to incorporate large quantities of components that are usually expensive.
The present inventors have found that a reduced amount of a particular nonionic active agent acts as a viscosity stabiliser for a fabric conditioning composition thereby providing a viscosity desired by consumers, even when included at very low levels (1.5% or less by weight in a fabric conditioning composition), when the composition is manufactured under certain conditions. In particular, it has been found that high-shear treatment of the composition below the phase transition temperature of the softener material provides the desired viscosity stability for a composition comprising said particular nonionic active agent.
WO 97/16516 discloses a softening composition comprising a cationic softener and a nonionic surfactant in a ratio of 1:2 to 4:1. There is no mention of formulating the composition under certain shear conditions.
EP 640121 discloses a composition comprising a diester quat and 0.1 to 30% of a viscosity/dispersibility modifier. There is no mention of hardened softening compounds.
EP 734433 discloses mixtures of hardened and partially unsaturated ester-linked quaternary ammonium materials. There is no mention of nonionic stabilising agents.
GB 2170829 discloses compositions comprising quaternary ammonium compounds and fatty alcohols in a ratio of 6:1 to 3:1. There is no mention of hardened quaternary ammonium compounds.
WO 99/29823 discloses a process for making a softener composition comprising forming a melt of a softener and optional additives, dispersing this in water, cooling to below the Krafft temperature of the softener and adding dye and nonionic material. There is no suggestion that the nonionic material can be incorporated before the mixture cools. Furthermore, there is no reference to high-shear milling.
EP 503221 discloses a composition comprising a cationic softener, a linear fatty alcohol ethoxylate and a highly branched fatty alcohol. There is no mention of a hardened cationic softener.
EP 309052 discloses compositions comprising 11 to 25% of a quaternised ester-amine, 0.1 to 10% of a linear alkoxylated alcohol with 1 to 10 alkylene oxide groups and 60% or more of a liquid carrier.